NAS Pans Current BLM Mustang Management

The Bureau of Land Management (BLM) should rely more on contraception than on roundups to effectively manage wild horse herds, according to NAS study results released this week.

Photo: Bureau of Land Management

The Bureau of Land Management (BLM) should rely more on contraception than on roundups to effectively manage wild horse herds, according to study results released this week.

The National Academy of Sciences/National Research Council (NAS/NRC) is an independent nonprofit group that advises government agencies on scientific issues. In 2010 the BLM asked NAS to review technical aspects of their wild horse and burro program, including science-based population estimation methods, annual herd growth rates, and population control measures. The BLM also asked the group to make recommendations for future wild horse and burro management techniques. The $1.5 million study began in 2011 and the results were released June 5.

In its report, the NAS said the population of wild horses under BLM care on public rangelands in Western states increases at an unsustainable rate of 15% to 20% annually. In managing its herds, the BLM has estimated the ideal number of horses each range can support, then reduced herd populations to meet that estimate by gathering and removing horses from the range. But according to the NAS report, the BLM has not used scientifically rigorous methods to estimate the horse and burro populations on each range or to model the effects of management actions on the animals under BLM care. The report said that the current methodology the agency uses also fails to assess the availability and use of forage on rangelands the animals occupy.

In addition, the report said the BLM fails to effectively use contraception tools—specifically porcine zona pellucida vaccines for mares and a chemical vasectomy vaccine in stallions—to achieve appropriate wild horse and burro population control. The report said that conclusion was based on delivery method, availability, efficacy, duration of effect, and the potential for side effects.

“Although applying these methods usually requires gathering horses and burros, that process is no more disruptive than the current method of population control—gathering and removal—without the further disruption of removing animals,” the NAS report said. “Considering all the current options these … methods, either alone or in combination, offer the most acceptable alternative to removing animals for managing population numbers.”

The NAS report also said the BLM failed to communicate how the agency determined, monitored, and adjusted ranges' appropriate management levels in a transparent way that the public could understand. The report further said the agency failed to communicate how science, new information, and environmental and social change figured into establishing range management levels.

Finally, when it comes to making policy decisions, the BLM must do better to bring together groups with diverse opinions about land use, ecology, and other sensitive issues, the report said: “BLM should develop an iterative process between public deliberation and scientific research and co-design the participatory process with representatives of the public."

Laura Leigh, president of the mustang advocacy group Wild Horse Education, said the results of the NAS report weren't news to her; she said her agency has long investigated and documented activities at BLM gathers and wild horse holding areas. But Leigh believes the report opens the door to meaningful conversation about wild mustang and burro management.

“We stand ready to assist in any way possible to create a management plan based on truth,” she said.

Meanwhile BLM Principal Deputy Director Neil Kornze welcomed the NAS report and said the agency is currently reviewing its findings.

“The BLM looks forward to reviewing the report in detail and building on the report’s findings and recommendations to meet the formidable challenges facing the agency in managing wild horses and burros,” Kornze said. “Our agency is committed to protecting and managing these iconic animals for current and future generations.”

Meanwhile, Kornze said that the NAS report will help the agency build on reforms implemented over the past several years to enhance program effectiveness.

“The BLM shares the (NAS study) committee’s view that, although no quick or easy fixes exist to this pressing issue, investments in science-based management approaches, exploring additional opportunities for population control, and increased transparency could lead to a more cost-effective program that manages wild horses and burros with greater public confidence,” Kornze said.